The Local 7 April 2021 09:21 CEST As Spain teeters on the edge of its fourth wave of the coronavirus, we take a look at the role new Covid strains are playing in rising infections in the country according to the latest government data. Viruses naturally change over time through the process of mutation, so the fact that several Covid variants have been detected by international scientists is no different from most other virus outbreaks. So far, three main strains of the coronavirus have been identified: B.1.1.7 (the variant first seen in the United Kingdom), B.1.351 (the strain first detected in South Africa) and P.1 (the variant first found in Brazil).